U.S. patent application number 12/194777 was filed with the patent office on 2010-02-25 for lofty, tackified nonwoven sheet and method of making.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Thomas E. Haskett, Robert J. Maki.
Application Number | 20100044909 12/194777 |
Document ID | / |
Family ID | 41136998 |
Filed Date | 2010-02-25 |
United States Patent
Application |
20100044909 |
Kind Code |
A1 |
Haskett; Thomas E. ; et
al. |
February 25, 2010 |
LOFTY, TACKIFIED NONWOVEN SHEET AND METHOD OF MAKING
Abstract
A method of making a tackified nonwoven sheet that includes
forming a densified, tackified web by providing a rebulkable
nonwoven fiber web and applying an adhesive to the nonwoven web.
The densified, tackified web is rebulked to an open, lofty form by
exposing the densified, tackified web to a temperature of at least
225.degree. F. Finally, a sheet is formed from the rebulked,
tackified web. In some embodiments, the so-formed sheet is a
cleaning wipe configured for picking up diverse debris such as
sand, dust, hair, and/or food particles. In other embodiments, the
method further includes the rebulked, tackified web having an
increased degree of loftiness as compared to a degree of loftiness
of the densified, tackified web prior to rebulking.
Inventors: |
Haskett; Thomas E.;
(Oakdale, MN) ; Maki; Robert J.; (Hudson,
WI) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
41136998 |
Appl. No.: |
12/194777 |
Filed: |
August 20, 2008 |
Current U.S.
Class: |
264/175 ;
264/258 |
Current CPC
Class: |
A47L 13/16 20130101;
D04H 1/64 20130101; D04H 1/50 20130101; A47L 25/005 20130101; D04H
1/587 20130101 |
Class at
Publication: |
264/175 ;
264/258 |
International
Class: |
B29C 65/52 20060101
B29C065/52; B29C 70/44 20060101 B29C070/44 |
Claims
1. A method of making a tackified nonwoven sheet, the method
comprising: forming a single-layer densified, tackified web
including: providing a rebulkable nonwoven fiber web, applying an
adhesive to the single-layer rebulkable nonwoven web; rebulking the
densified, tackified web by exposing the single-layer densified,
tackified web to a temperature of at least 225.degree. F. to
generate a single-layer rebulked, tackified web having an open,
lofty form; and forming a cleaning wipe from the single-layer
rebulked, tackified web.
2. The method of claim 1, wherein the densified, tackified web has
a first thickness and the rebulked, tackified web has a second
thickness, the second thickness being greater than the first
thickness.
3. The method of claim 1, wherein the densified, tackified web has
a first degree of loftiness, and the rebulked, tackified web has a
second degree of loftiness, the second degree of loftiness being
greater than the first degree of loftiness.
4. The method of claim 1, wherein the densified, tackified web has
a first average spacing between adjacent fibers and the rebulked,
tackified web has a second average spacing between adjacent fibers,
the second average spacing between adjacent fibers being greater
than the first average spacing between adjacent fibers.
5. The method of claim 1, wherein providing a rebulkable nonwoven
fiber web includes: entangling a plurality of fibers; and
compressing the entangled fibers.
6. The method of claim 5, wherein the rebulkable nonwoven fiber web
has a first thickness following compressing, and the rebulked,
tackified web has a second thickness, the second thickness being
greater than the first thickness.
7. The method of claim 1, wherein compressing the entangled fibers
includes: calendering the entangled fibers.
8. The method of claim 1, wherein applying an adhesive includes:
applying a water-based pressure sensitive adhesive composition to
the nonwoven fiber web.
9. The method of claim 8, wherein the pressure sensitive adhesive
composition includes at least 25% water and an acrylate
adhesive.
10. The method of claim 1, wherein the method includes the absence
of applying a compressive force to the tackified web immediately
after the step of applying the adhesive and prior to the step of
rebulking the densified, tackified web.
11. The method of claim 1, wherein rebulking the densified,
tackified web includes exposing the densified, tackified web to a
temperature of at least 350.degree. F.
12. The method of claim 1, wherein conveying a continuous length of
the densified, tackified web includes moving the tackified web
through the oven at a conveyor speed of at least 5 feet per
minute.
13. The method of claim 1, wherein rebulking the densified,
tackified web includes conveying a continuous length of the
densified, tackified web through an oven heated to a temperature of
at least 300.degree. F.
14. The method of claim 13, wherein the oven is heated to a
temperature of at least 350.degree. F.
15. A method of making a tackified nonwoven sheet, the method
comprising: forming a densified, tackified web including: providing
a rebulkable nonwoven fiber web, applying an adhesive to the
rebulkable nonwoven web; rebulking the densified, tackified web by
exposing the densified, tackified web to a temperature of at least
225.degree. F. to generate a rebulked, tackified web having an
open, lofty form; and forming a cleaning wipe from the rebulked,
tackified web, wherein there is an absence of applying a
compressive force to the tackified web immediately after the step
of applying the adhesive and prior to the step of rebulking the
densified, tackified web.
16. The method of claim 15, wherein at least some of the adhesive
is exposed at a working surface of the cleaning wipe.
17. The method of claim 15, wherein there is an absence of
additional densified, tackified webs applied to the densified,
tackified web.
18. The method of claim 15, wherein the densified, tackified web is
a single layer web.
Description
BACKGROUND
[0001] The present disclosure relates to adhesive-loaded, nonwoven
fiber web-type sheet constructions and methods of manufacture. More
particularly, it relates to nonwoven sheet constructions, such as
cleaning wipes for removing diverse debris from surfaces,
incorporating an adhesive and exhibiting enhanced loftiness, along
with methods of making the same.
[0002] Adhesive-loaded, nonwoven sheet articles are commonly
employed for a plethora of applications. For example, such articles
can be used with filtration devices for filtering particles and/or
odors from air. Additionally, adhesive nonwoven sheets can be
provided as a cleaning wipe to clean debris from surfaces. As a
point of reference, general cleaning wipe articles, or wipes, are
used either by hand or attached to a tool such as a mop handle to
move dirt, dust, etc. in a desired direction where an adhesive is
incorporated into the wipe, the adhesive assists in retaining both
small and large particles of dirt and other debris within the wipe
structure. However, the adhesive may undesirably adhere to the
surface being cleaned. Further, the adhesive may cause the wipe to
overtly drag as the wipe is moved along the surface being
cleaned.
[0003] Some efforts have been made to provide a cleaning wipe
having a tacky or adhesive characteristic, yet with a lessened
adhesive "feel" and surface drag. Such efforts have generally
focused on the careful selection of the type and amount of the
adhesive material(s), and/or the pattern of application of the
adhesive as a means for reducing drag so as to improve particle
pick-up while maintaining the ability of the cleaning wipe to glide
across the surface being cleaned. While potentially viable, these
techniques entail fairly complex machinery and process controls,
and thus higher manufacturing costs. Further, the wipes resulting
from such processing techniques are fairly dense. That is to say,
the fibers of the adhesive-loaded nonwoven web are compacted
relative to one another, thereby limiting the amount and/or size of
particles that can be retained within the wipe's thickness.
[0004] In light of the above, a need exists for improved methods of
making tackified, nonwoven fiber sheet products such as cleaning
wipes. Further, a need exists for a low-cost, tackified, nonwoven
fiber cleaning wipe exhibiting enhanced loftiness and low drag as
compared to existing cleaning wipes.
SUMMARY
[0005] Some aspects in accordance with principles of the present
disclosure relate to a method of making a tackified nonwoven sheet.
The method includes forming a densified, tackified web by providing
a rebulkable nonwoven fiber web and applying an adhesive to the
nonwoven web. The densified, tackified web is rebulked to an open,
lofty form by exposing the densified, tackified web to a
temperature of at least 225.degree. F. Finally, a sheet is formed
from the rebulked, tackified web. In some embodiments, the
so-formed sheet is a cleaning wipe configured for picking up
diverse debris such as sand, dust, hair, and/or food particles. In
other embodiments, the method further includes the rebulked,
tackified web having an increased degree of loftiness as compared
to a degree of loftiness of the densified, tackified web prior to
rebulking. In yet other embodiments, rebulking the densified,
tackified web includes conveying a continuous length of the
densified, tackified web through an oven heated to a temperature of
at least 350.degree. F. and at a conveyor speed of at least 5 feet
per minute.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic, perspective view of a tackified
nonwoven sheet in accordance with the present disclosure;
[0007] FIG. 2 is a schematic illustration, with portions shown in
block form, of a system and method in accordance with the present
disclosure for making a tackified nonwoven sheet;
[0008] FIG. 3A is a simplified cross-sectional view of an example
densified, tackified sheet provided at an intermediate stage of the
system and method of FIG. 2; and
[0009] FIG. 3B is a simplified cross-sectional view of the sheet of
FIG. 3A following rebulking by the system and method of FIG. 2, and
as a rebulked, tackified sheet.
DETAILED DESCRIPTION
[0010] One embodiment of a sheet or wipe 20 in accordance with
principles of the present disclosure is provided in FIG. 1. As a
point of reference, the sheet 20 can be sized and/or shaped for
various end-use applications, such as air filtration. In addition,
the sheet 20 construction is highly useful for cleaning
applications, and thus is interchangeably referred to as a "wipe"
or "cleaning wipe" throughout this specification. In general terms,
the cleaning wipe 20 includes a web construction 22 including a
nonwoven fiber web 24 and an adhesive or tacky material (unnumbered
in FIG. 1). The nonwoven fiber web 24 defines or forms a working
surface 26 opposite a second surface 28 (with the second surface 28
being generally hidden in the view of FIG. 1). The term "working
surface" is in reference to a side of the cleaning wipe 20 that is
otherwise presented to and guided (or "wiped") across a surface to
be cleaned. An intermediate region 30 (referenced generally in FIG.
1) is defined between the outer surfaces 26, 28. With these
designations in mind, the adhesive material coats individual fibers
comprising the fiber web 24, providing a tackiness to the cleaning
wipe 20. In this regard, the resultant web construction 22 exhibits
a relatively high degree of loftiness as described below. For ease
of illustration, the outer surfaces 26, 28 are shown in FIG. 1 as
being substantially flat; it will be recognized that this
representation does not reflect a void volume provided in
embodiments of the present disclosure. Further, while the cleaning
wipe 20 is shown in FIG. 1 as assuming a substantially planar form,
other shapes are acceptable. For example, the cleaning wipe 20 can
be rolled or folded onto itself to form a roll.
[0011] The term "degree of loftiness" as used in the specification
is in reference to the spacing or "openness" of fibers otherwise
forming the surface/area/volume in question. For example, a first
surface/area/volume with fewer fibers per unit area or volume as
compared to a second surface/area/volume comprised of the same
denier fibers is considered to have a higher degree of loftiness.
Alternatively, degree of loftiness can be defined in terms of bulk
density. "Bulk density" is the weight of a given web per unit
volume. The web thickness can be measured in many ways; one
accurate method employs an optical scanning technique.
[0012] Various, acceptable material(s) and formats of the nonwoven
fiber web 24 and the adhesive are provided below. More generally,
the nonwoven web 24 is, in some embodiments, rebulkable. Rebulkable
nonwoven webs may be converted (at least once) from a densified or
compressed state (i.e., a higher density, lower soft state) to a
rebulked or less compressed state (i.e., a lower density, higher
soft state). The process of converting the rebulkable web from the
densified state to the rebulked state is referred to as
"rebulking." Typically, the process of rebulking the web is
accomplished by heating the web. Heating the web softens at least
some of the bonds formed between fibers of the web. This allows at
least some of the fibers to expand toward their original length,
thereby at least partially restoring at least a portion of the
original bulk to the nonwoven web. The adhesive applied to the
nonwoven web 24 is selected to not overtly interfere with rebulking
of the nonwoven web 24.
[0013] As described below, the web construction 22 includes the
nonwoven web 24 in rebulked form and exhibits an elevated degree of
loftiness relative to the type(s)/size(s) of fibers from which the
nonwoven web 24 is constructed and a type and volume of an applied
adhesive as compared to prior wipes incorporating similar
materials. In some embodiments, these improvements are imparted via
one or more of the methods of making disclosed herein. For example,
FIG. 2 provides a simplified illustration of a process and system
for making the cleaning wipe 20. The system includes a web forming
station 40, an adhesive station 42, and a rebulking station 44. The
stations 40-44 can assume a variety of forms and can be arranged to
provide a continuous manufacturing process as shown, or one or more
of the stations 40-44 can be provided separately such that
processing from one station to another is discontinuous.
Regardless, and in general terms, a rebulkable, nonwoven web 50 is
generated at the web forming station 40. Adhesive is applied to the
rebulkable nonwoven web 50 at the adhesive station 42. As part of
the processing at the web forming station 40, the adhesive station
42 and/or at another station (not shown) "upstream" of the
rebulking station 44, the rebulkable nonwoven web 50 is densified
(e.g., compressed). As a result, a densified, tackified nonwoven
web 52 exits from the adhesive station 42, and is then passed
through the rebulking station 44 to effectuate rebulking of the
densified, tackified web 52. A rebulked, tackified web 54 exits
from the rebulking station 44, and can serve as the web
construction 22 (FIG. 1), or can be further processed (e.g., cut)
to form the desired wipe 20 (FIG. 1).
[0014] The web forming station 40 can include one or more devices
typically used to form a nonwoven web from fibers. In general
terms, however, the rebulkable nonwoven web 50 can be formed in a
variety of fashions known in the art in which individual fibers are
entangled with one another (and optionally bonded) in a desired
fashion. For example, the rebulkable nonwoven web 50 can be formed
by carding, spun bond, melt blown, air laid, wet laid,
needle-tacking, etc. The rebulkable nonwoven web 50 can be
consolidated by any known technique such as, for example,
hydroentanglement, thermal bonding (e.g., calender or through air),
chemical bonding, etc. Thus, the web forming station 40 can include
two or more in-line sub-station components, such as (by way of but
one non-limiting example) a combining sub-station at which loose
fibers are combined together, a needle-tacking sub-station at which
a web precursor is needle-tacked, and/or a melt-bonding sub-station
at which the web precursor is melt-bonded.
[0015] In some embodiments, the selected web forming station 40 is
further adapted to compress the formed rebulkable nonwoven web 50.
This compression serves to densify the rebulkable nonwoven web 50.
Thus, the web forming station 40 can include appropriate equipment
for compressing the rebulkable nonwoven web 50 following carding,
for calendering the nonwoven web 50, etc. For example, where the
web forming station 40 is configured to form the rebulkable
nonwoven web 50 via melt-bonding, compression of the web 50 can be
effectuated by passing the rebulkable nonwoven web 50 between
opposing belts that compress and density the rebulkable nonwoven
web 50. The rebulkable nonwoven web 50 can be cooled in this state
of compression to "set" the rebulkable nonwoven web 50 in its
densified state. Regardless, the rebulkable nonwoven web 50 can be
uniformly or non-uniformly densified at the web forming station 40.
Even further, densification or compression of the rebulkable
nonwoven web 50 can occur at the adhesive station 42 such that a
compression sub-station component need not be included with the web
forming station 40.
[0016] Where desired, the formed rebulkable nonwoven web 50 can be
subjected to further processing prior to application of adhesive,
such as printing indicia to one or both of the outer surfaces 56,
58 (e.g., trademark, user information, etc.), a colorant applied, a
surface pattern imparted, etc. Even further, the rebulkable
nonwoven web 50 can optionally be extrusion coated with plastic
hooks for desired combination of properties.
[0017] Regardless of the resultant form or appearance of the
rebulkable nonwoven web 50, an adhesive is applied to the web 50 at
the adhesive station 42. Adhesive compositions useful with the
present disclosure are described below. In general terms, however,
the adhesive is, in some embodiments, a water-based pressure
sensitive adhesive, and can be applied to the rebulkable nonwoven
web 50 in a variety of fashions. For example, the adhesive can be
roll-coated, pattern-coated, or one-side (or "kiss") coated,
spray-coated, screen-printed, etc. The volume of applied adhesive
in combination with the application technique employed with the
adhesive station 42 is selected, in some embodiments, to saturate
the rebulkable nonwoven web 50. Alternatively, only partial
saturation can be effectuated. With this alternative approach, the
adhesive is applied to one of the surfaces 56, 58 (in some
embodiments the surface 56 or 58 intended to serve as the working
surface 26 (FIG. 1)) of the rebulkable nonwoven web 50 to better
ensure existence of at least some adhesive at the working surface
26 to assist in collecting debris during use of the finally formed
wipe.
[0018] Application of the adhesive at the adhesive station 42 may
naturally cause the rebulkable nonwoven web 50 to partially densify
(e.g., the collective weight of the adhesive may cause the
rebulkable nonwoven web 50 to self-compress, the adhesive may cause
individual fibers to more closely bond with one another, etc.).
Under at least these circumstances, then, the web forming station
40 need not include a separate compression sub-station.
Alternatively or additionally, the adhesive station 42 can include
one or more devices for compressing and densifying the rebulkable
nonwoven web 50.
[0019] Regardless of the manner in which the adhesive is applied,
the densified, tackified web 52 is generated as shown in FIG. 2. As
used in the specification, reference to a "densified, tackified
web" is with respect to an intermediate stage of manufacture in
which adhesive has been applied to a densified, rebulkable nonwoven
web, but no additional manufacturing steps have been performed. For
example, no additional web(s) are applied to the densified,
tackified web 52; the densified, tackified web 52 is not folded
onto itself; etc. With this in mind, the densified, tackified web
52 is rebulked at the rebulking station 44. More particularly, the
densified, tackified web 52 is exposed or subjected to a heated
environment having a temperature sufficient to promote re-lofting
(or rebulking) of the densified, tackified web 52. Typically, the
rebulking station 44 includes an oven. With water-based pressure
sensitive adhesives, it has been found that temperatures of at
least 225.degree. F. cause desired rebulking (and drying) of the
densified, tackified web 52.
[0020] The rebulking temperature can, in some embodiments, be
greater than 225.degree. F. For example, in some embodiments, the
densified, tackified web 52 is subjected to, at the rebulking
station 44, a temperature of at least 300.degree. F., in other
embodiments at least 325.degree. F., in yet other embodiments at
least 350.degree. F. Further, the densified, tackified web 52 is,
in some embodiments, continuously conveyed relative to the
rebulking station 44. In other words, a continuous length of the
densified, tackified web 52 is continuously conveyed through, for
example, an oven. Though various other parameters may impact
optional dwell times (e.g., oven length, temperature, ambient
humidity, and percentage of solids of the adhesive) for causing
rebulking and drying of the densified, tackified web 52, conveyor
line speeds on the order of at least 5 feet per minute at oven
temperatures of at least 225.degree. F. are acceptable, although
other processing speeds and/or temperatures can be employed.
[0021] In addition to effectuating an increase in the loftiness of
the densified, tackified web 52, the rebulking step promotes a more
uniform distribution of the applied adhesive to the fibers
comprising the rebulkable nonwoven web 50. More particularly, as
the fibers extend relative to one another with rebulking (thus
establishing a greater spacing between adjacent fibers), the
applied adhesive will naturally distribute itself in a relatively
uniform manner throughout the interior of the nonwoven web 50
(i.e., the intermediate region 30 of FIG. 1). Alternatively,
however, a less uniform adhesive distribution can also be
accomplished by partially applying the adhesive to only one side 56
or 58 of the nonwoven web 50.
[0022] Following processing at the rebulking station 44, the
rebulked, tackified web 54 results. Where desired, the rebulked,
tackified web 54 can be subjected to further processing as desired.
For example, the rebulked tackified web 54 can be patterned to a
uniform geometry by an appropriate mechanism. Further, the
rebulked, tackified web 54 can be cut to a desired size, shape,
etc. Regardless, the cleaning wipe 20 (FIG. 1) is formed from the
rebulked, tackified web 54 (that is otherwise akin to the web
construction 22 of FIG. 1).
[0023] The enhanced loftiness effectuated by the above-described
rebulking in the presence of heat can be characterized by
referencing a degree of loftiness prior to and following rebulking.
For example, and with reference to the schematic illustrations of
FIGS. 3A and 3B, the densified, tackified web 52 has a thickness
t.sub.1. Upon exposing the densified, tackified web 52 to heat as
described above, the resultant rebulked, tackified web 54 has a
thickness t.sub.2, with the rebulked thickness t.sub.2 being
greater than the thickness t.sub.1 prior to rebulking by at least
10%.
[0024] The openness or loftiness achieved with the above-described
methods of making are a function of the materials and amounts
selected for the rebulkable nonwoven web 50 and the adhesive. For
example, the size and/or weight of the selected fibers and/or the
volume or composition of the applied adhesive will inherently
affect the resultant loftiness achieved when subjecting the
densified, tackified web 52 to the temperatures described above.
With this in mind, the fibers comprising the rebulkable nonwoven
web 50 (and thus of the nonwoven web 24 of FIG. 1) are synthetic or
manufactured, but alternatively can include natural fibers. As used
herein, the term "fiber" includes fibers of indefinite length
(e.g., filaments) and fibers of discrete length (e.g., staple
fibers). The fibers used in connection with the rebulkable nonwoven
web 50 may be multicomponent fibers. The term "multicomponent
fiber" refers to a fiber having at least two distinct
longitudinally co-extensive structured polymeric domains in the
fiber cross-section, as opposed to blends where the domains tend to
be dispersed, random, or unstructured. In some embodiments, two or
more differing types of fibers are employed (e.g., a multiplicity
of a first fiber and a multiplicity of a second fiber). Regardless,
useful fibrous materials include, for example, polyesters,
polyamides, polyimides, nylon, polyolefins (e.g., polypropylene and
polyurethane), rayon, melty fiber, etc., of any appropriate fiber
length and denier, and mixtures thereof. Further, some or all of
the fibers can have special treatments to enhance hydrophilic
properties, such as additives including super-absorbing gel
polymers; also, powder(s) or fiber(s) such as, but not limited to,
rayon, cotton, and cellulose, can be added to enhance
liquid-holding capacity.
[0025] Small denier size staple fibers (e.g., 3 d-15 d) provide the
resultant nonwoven web 24 (FIG. 1) with smaller pore sizes and more
surface areas compared to a fiber web made with larger denier
fibers (e.g., 20 d-200 d) that otherwise provides the nonwoven web
24 with larger pore sizes and less surface area. The small denier
fiber webs are best suited for cleaning surfaces contaminated with
fine dust and dirt particles, whereas the large denier fiber webs
are best suited for cleaning surfaces contaminated with larger dirt
particles such as sand, food crumbs, lawn debris, etc. The larger
pore sizes of the larger denier staple fibers allow the larger
contaminant particles to enter, and be retained by, the matrix of
the fiber web. The nonwoven web 24 of the present disclosure can
include one or both of the small and/or large denier fibers that
may or may not be staple fibers. In some embodiments, the nonwoven
web 24 includes crimped, high heat distortion fibers. Preferably,
however, to ensure desired loftiness, a majority of the fibers of
the nonwoven web 24 are of a larger denier (e.g., at least 20
denier, more preferably at least 25 denier).
[0026] The adhesive can also assume a variety of forms, and in some
embodiments, is or includes a water-based pressure sensitive
adhesive. Pressure sensitive adhesives are normally tacky at room
temperature and can be adhered to a variety of surfaces by
application of light finger pressure. An adhesive bond is developed
by pressing a second surface (or individual particles of a second
material such as, for example, dust, dirt, crumbs, or other debris)
against the pressure sensitive adhesive coated material.
Alternatively, suitable adhesives for use with the present
disclosure include any that are capable of being tacky at room
temperature, including both adhesives that are initially tacky and
those that are initially non-tacky but which can be activated to
become tacky. Suitable adhesives include any pressure sensitive
adhesives including materials based on acrylates, silicones,
poly-alpha-olefins, polyisobutylenes, rubber block copolymers (such
as styrene/isoprene/styrene and styrene/butadiene/styrene block
copolymers, styrene/butadiene/rubbers, synthetic isoprenes, natural
rubber, and blends thereof). While the pressure sensitive adhesives
useful with the present disclosure are preferably water based, in
other embodiments, the pressure sensitive adhesives may be coated
from solvents, radiation polymerized, or hot melt processed. These
pressure sensitive adhesives may or may not be cross-linked.
Cross-linking can be done by well-known methods, including
chemical, ionic, physical, or radiation-induced processes. Other
useful adhesive compositions may include, for example, polyvinyl
ethers, ethylene containing copolymers such as ethylene vinyl
acetate, ethylacrylate, and ethylmethacrylate, polyurethanes,
polyamides, polyepoxides, polyvinylpyrrolidones, and copolymers
thereof, polyvinyl alcohols, and copolymers thereof, polyesters,
and combinations thereof.
[0027] A general description of useful pressure sensitive adhesive
compositions can be found in the Encyclopedia of Polymer Science
and Engineering, Volume 13, Wiley-Interscience Publishers (New York
1988). As discussed in the Handbook of Pressure Sensitive Adhesive
Technology, Second Edition (D. Satas, Editor Van Nostrin Reinhold,
New York, 1989), these adhesives may be based on polymers like
natural rubber, acrylates, styrene-budadienes, and vinyl ethers.
Further, the elastomeric block copolymers of the adhesive
composition may be formulated with tackifying resins (tackifiers)
to improve adhesion and introduce tack into the pressure sensitive
adhesive.
[0028] Suitable tackifier resins are described in the Handbook of
Pressure Sensitive Adhesive Technology referenced above, and can
include rosin esters, terpenes, phenols, and aliphatic, aromatic,
or mixtures of aliphatic and aromatic synthetic hydrocarbon monomer
resins. The tackifier components useful in block copolymer adhesive
compositions can be solid, liquid, or a blend thereof. Suitable
solid tackifiers include rosin, rosin derivatives, hydrocarbon
resins, polyterpenes, coumarone indenes and combinations thereof.
Suitable liquid tackifiers include liquid hydrocarbon resins,
hydrogenated liquid polystyrene resins, liquid polyterpenes, liquid
rosin esters, and combinations thereof. Many tackifiers are
commercially available, and optimum selection thereof can be
accomplished by one of ordinary skill in the adhesive compounding
art.
[0029] The adhesive composition can also include additives such as,
for example, plasticizers, diluents, fillers, antioxidants,
stabilizers, pigments, cross-linking agents, and the like.
[0030] The amount of adhesive that is applied to the rebulkable
nonwoven web 50 depends on a number of factors, including the
tackiness of the adhesive, the degree to which the adhesive adheres
to surfaces (and thus makes wiping difficult), and other such
factors. In some embodiments, the amount of adhesive should be
sufficient enough for the resultant wipe 20 (FIG. 1) to capture
both small and large particles of various shapes and consistencies,
such as lint, dust, hair, sand, food particles, and the like,
without having excess adhesive that could create drag and make
wiping difficult and/or that could be transferred to the surface
being cleaned. With this in mind, the wipe constructions in
accordance with the present disclosure will typically include from
about 5 weight % to about 200 weight % of adhesive, more typically
from about 10 weight % up to about 130 weight %.
[0031] Due to the enhanced loftiness and uniform adhesive
distribution provided by the above methods, the resultant wipe 20
can incorporate an increased adhesive loading as compared to
existing adhesive laden, nonwoven wipes. As a result, the cleaning
wipe 20 more readily retains debris as compared to wipes of similar
construction/materials. Further, due to the enhanced loftiness, a
greater volume of debris can be retained, while at the same time
exhibiting a reduced drag value. With any of the above-described
methods, by varying one or more the tacky material type and/or
basis weight, fiber denier and/or basis weight, temperature, line
speed, etc., the resultant cleaning wipe 20 can be formed to
provide certain desired characteristics. Further, multiple ones of
the so-formed cleaning wipes 20 can be releasably secured to one
another in a back-to-back fashion (such as by an appropriate
adhesive or other tacky material). With this configuration,
individual cleaning wipes can be successfully stripped from a
multiple layer assembly before, during, or after use in cleaning.
Regardless, methods of the present disclosure provide marked
improvements over previous designs by generating a lofty, tackified
cleaning wipe in a simple and rapid manner highly amenable to mass
production.
EXAMPLES
[0032] Features and advantages of the present disclosure are
further illustrated in the following Examples. It is to be
expressly understood, however, that the particular materials and
amounts used, as well as other conditions and details are not to be
construed in a manner that would unduly limit the scope of this
disclosure.
Example No. 1
[0033] An example cleaning wipe was prepared in accordance with
aspects of the present disclosure by first providing a fiber blend
consisting of (1) 50% (weight percent) 15 denier.times.2.0 inch
polyester staple fiber (available under the trade designation KoSa
T-295 from Invista of Charlotte, N.C.), (2) 30% (weight percent) 25
denier.times.1.5 inch polyester staple fiber (available under the
trade designation 694 P from Wellman, Inc., of Fort Mill, S.C.),
and (3) 20% (weight percent) 4 denier.times.2 inch polyester melty
staple fiber (available under the trade designation LMF from Huvis
of Seoul, Korea). The fiber blend was carded to a basis weight of
54 gsm. The carded web was then calendered on a calender device
having two smooth steel rolls. The rolls were heated to 245.degree.
F., and set to a gap of 0.020 inch. The calender device was run at
a calender pressure of 100 psi, and employed to pre-bond the
web.
[0034] A liquid adhesive composition consisting of a liquid acrylic
adhesive at 17.5% solids (available under the trade designation
RD-914 from 3M Company of St. Paul, Minn.), 0.5% surfactant
(available under the trade designation OT-75 from Union Carbide of
Danbury, Conn.), and 0.1% defoamer agent (available under the trade
designation Advantage Defoamer 1512 from Hercules, Inc. of
Wilmington, Del.) was prepared. The adhesive composition was roll
coated to the calendered web by a roll coater having a steel
gravure bottom roll and a rubber top roll, maintained at a nip
pressure of 60 psi. The web was roll coated to saturation.
Following application of the adhesive composition, the coated web
was re-bulked and dried in a through air oven set at a temperature
of 400.degree. F. and at a typical line speed of 20 feet per
minute. The re-bulked web was then collected on a surface winder
for subsequent formation as a cleaning wipe (e.g., cutting
operation), and had a finish weight after drying of 70 gsm.
Example No. 2
[0035] A 60 gsm basis weight carded web available from Precision
Custom Coatings, LLC, of Totowa, N.J. was provided, using the same
fiber blends and denier sizes (30% 25 denier PET, 50% 15 denier
PET, & 20% 4 denier PET Melty), but different manufacturers of
Example No. 1 above. The web was carded, through air bonded, and
compressed in one step. In a second step a liquid adhesive
composition consisting of 20% solids RD -914 (available from 3M
Company of St. Paul, Minn.), 0.5% OT-75 surfactant (available from
Union Carbide of Danbury, Conn.), and 0.1% 1512 defoamer (available
from Hercules of Wilmington, Del.) was prepared and roll coated to
the carded web. The coated cloth was rebulked and dried in an oven
as was Example 1. The dried coated cloth weight was 70 gsm.
[0036] The re-bulked, tackified webs and wipes of Example Nos. 1
and 2 exhibited sufficient web openness for dust holding capacity,
low drag, and good re-bulking or lofting in the drying oven.
[0037] The re-bulked, tackified webs and wipes of Example Nos. 1
and 2 were subjected to testing as described below, as was a
Comparative Example in the form of a dry floor cloth available from
3M Company under the trade name 3M Super Cling Dry Floor Cloth,
Catalog No. 8001. The webs and wipes as tested had weights and
caliper characteristics as set forth in Table 1 below.
TABLE-US-00001 TABLE 1 Basis Wt. Adhesive Total Wt. Caliper Caliper
Sample (gsm) Wt. (gsm) (gsm) (in) (mm) Example 1 54 14 68 0.125
3.18 Example 2 60.0 9.5 69.7 0.113 2.87 Comparative 61 5 66 0.062
1.58 Example
Test Methods
Drag Measurement
[0038] A model 225-235 Friction Tester, available from
Thwing-Albert Instrument Company (Philadelphia, Pa.), was equipped
with a 500 lb load plate (3 inch.times.5 inch), and set to a speed
of 110 inch (279.4 cm) per minute and a time of 5 seconds. A
rectangular sheet of black glass was cut to fit the Friction
Tester, and marked with a 4 inch long test area. The glass was
cleaned using glass cleaner. Individual test samples were prepared
as 6 inch.times.8 inch sections of the wipe to be tested, folded in
half (4 inch.times.6 inch surface area), and placed on the test
fixture. The friction tester was run, and the kinetic coefficient
of friction (KI) and static coefficient of friction (ST) values
were recorded.
Sand and Dust Removal Test--Flat
[0039] Sand and dust removal was measured by distributing a mixture
of 0.5 gram sand (90-177 micron mean diameter) and 0.15 gram JIS
dust (with a combined weight of the sand and dust collectively
designated as W.sub.1) on the surface of a 1.33 meter square floor.
A test sample cloth was weighed and recorded (W.sub.2), and then
attached to a flat head of a mop available from 3M Company of St.
Paul, Minn. (ScotchBrite.TM. High Performance Sweeper Mop). The mop
head was attached to the mop handle. The test sample was first
pushed and pulled once over the entire flooring area (i.e., one
pass over every area of the flooring that had sand and dust on it)
with minimal pressure applied to the handle of the mop, and then
pushed around the edge of the flooring area in a counter-clockwise
motion, turning the mop head at the corners. The test sample cloth
was then carefully removed from the handle and its weight was
measured (W.sub.3). The weight percent of the sand and dust removed
by the test sample from the surface was calculated as follows:
% sand and dust removed=[(W.sub.3-W.sub.2)/W.sub.1].times.100.
Hair Removal Test--Flat
[0040] Hair removal was measured in accordance with the Sand and
Dust Removal Test--Flat, except that 0.2 gram of pet hair (W.sub.1)
was distributed onto the flooring area rather than sand and
dust.
Sand and Dust Removal Test--Contour
[0041] Sand and dust removal was measured according to the Sand and
Dust Removal Test--Flat except that the wipe samples were attached
to a contour or angle glider head rather than a flat mop head. The
contour head has a triangular-like shape, thus providing three
edges for cleaning. The contour head is described in U.S.
application Ser. No. 11/953,542, filed Dec. 10, 2007, and entitled
"Cleaning Tool" and the entire teachings of which are incorporated
herein by reference. Further, the combination of sand and hair
distributed onto the flooring area was 0.8 gram sand (90-177 micron
mean diameter) and 0.2 gram JIS dust, and three allotments of the
sand and hair combination were prepared. The testing consisted of
distributing a first allotment of the sand and hair combination
onto the flooring area, passing the test sample along the first
edge of the head over the flooring area as described in the Sand
and Dust Removal Test--Flat, and repeating the procedure for the
second and third allotments along the second and third edges of the
head, respectively (e.g., distributing a second allotment of the
sand and hair combination onto the flooring area, passing the test
sample along the second edge of the head over the flooring area,
etc.). The test sample was thus exposed to a total of 3.0 grams
sand and dust (W.sub.1), and the test sample was weighed (W.sub.3)
after the third pass.
Hair Removal Test--Contour
[0042] Hair removal was measured according to the Sand and Dust
Removal Test--Contour, except that three allotments of 0.3 gram pet
hair were prepared and distributed onto the flooring area in
succession, exposing the test sample to 0.9 gram pet hair in total
(W.sub.1).
Sand Removal Test A--Contour
[0043] Sand removal was measured according to the Sand and Dust
Removal Test--Contour except that three allotments of 1.0 gram sand
(90-177 micron mean diameter), rather than a combination of sand
and hair, were prepared and distributed onto the flooring area in
succession, exposing the test sample to 3.0 grams sand in total
(W.sub.1).
Sand Removal Test B--Contour
[0044] Sand removal was measured according to the Sand and Dust
Removal Test--Contour except that three allotments of 2.0 grams
sand (90-177 micron mean diameter), rather than a combination of
sand and hair, were prepared and distributed onto the flooring area
in succession, exposing the test sample to 6.0 grams sand in total
(W.sub.1).
Sand Removal Test C--Contour
[0045] Sand removal was measured according to Sand and Dust Removal
Test--Contour except that three allotments of 3.0 grams sand
(90-177 micron mean diameter), rather than a combination of sand
and hair, were prepared and distributed onto the flooring area in
succession, exposing the test sample to 9.0 grams sand in total
(W.sub.1).
Dust Removal Test--Contour
[0046] Dust removal was measured according to the Sand and Dust
Removal Test--Contour, except that three allotments of 0.67 gram
JIS dust, rather than a combination of sand and hair, were prepared
and distributed onto the flooring area in succession, exposing the
test sample to 2.0 grams JIS dust in total (W.sub.1).
Large Particulate Removal Test--Contour
[0047] Large particulate removal was measured according to the Sand
and Dust Removal Test--Contour, except that three allotments of
0.25 gram crushed Cheerios.TM., rather than a combination of sand
and hair, were prepared and distributed onto the flooring area in
succession, exposing the test sample to 0.75 gram crushed Cheerios
in total (W.sub.1).
[0048] The measured drag coefficient of friction for Example Nos. 1
and 2 and the Comparative Example are provided in Table 2
below.
TABLE-US-00002 TABLE 2 Static Coefficient Sample of Friction
Kinetic Coefficient of Friction Example 1 0.793 0.563 Example 2
0.642 0.470 Comparative Example 0.631 0.500
[0049] The results of the Sand and Dust Removal Test--Flat and the
Hair Removal Test--Flat are provided in Table 3 below.
TABLE-US-00003 TABLE 3 % Sand & Dust Removal Sample (Flat) %
Hair Removal (Flat) Example 1 93.83 68.18 Example 2 95.11 73.99
Comparative Example 66.02 65.31
[0050] Results of the various removal tests using the contour
glider head are provided in Table 4 below.
TABLE-US-00004 TABLE 4 % % Sand % Hair Particulate % Dust &
Dust % Sand % Sand % Sand Removal Removal Removal Removal Removal A
Removal B Removal C Sample (Contour) (Contour) (Contour) (Contour)
(Contour) (Contour) (Contour) Example 1 85 87 58 88 98 98 92.3
Example 2 77.6 68.6 61.0 88.1 98.8 97.8 89.0 Comparative 44.4 52.0
21.8 48.8 36.0 38.0 31.1 Example
[0051] Comparison of performance between Example Nos. 1 and 2 and
the Comparative Example showed that the presence of adhesive has a
large effect on debris removal with minimal effect on drag.
[0052] Although the present disclosure has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes can be made in form and detail without
departing from the spirit and scope of the present disclosure.
* * * * *